Cut and squish tomatoes until they are more of a puree. Add tomato, diced onion, tomato paste, and sugar to saucepan. Flavor with garlic, salt, pepper, and oregano as much as you like. (I go light on the salt because canned tomatoes tend to have a lot of sodium, and then I add generous amounts of garlic and oregano for full flavor.) Simmer for at least 30 minutes, and stir frequently.

Come back tomorrow for the rest of the casserole instructions — cooking the eggplant and layering the casserole.